Something about CS. Switching out of it doesn't incur CD. If you accidentally (or purposefully) drop it you can turn on right away. It can also be queued. If you execute it even well during previous cast, it falls of/gets on without delay between the casts. So yes. It is quite possible to drop your CS when still casting previous damage spell, cast your heal, then activate CS again during the heal cast time and cast your next damage spell with no lost GCDs whatsoever. However, it -has- cooldown the other way around, you can't drop it immediately when you have activated it.
Guess this constitutes part of the stance dance. Know how to weave it in between the casts to not loose time for the chance.
About usability of SS, tend to use it heavily where ever there are Nix type monsters. Their pull attack is mitigated with Stoneskin.